Flood Risks
I went to a talk last week hosted jointly by the Richmond Society and the River Thames Society on the subject of Flood Risk. Here are a few notes of the bits that stuck in my memory. The first bit being that the EA now takes Molesey Lock at Hampton Court, rather than Teddington, to be the limit of the tidal Thames, since the weir at Teddington so often overflows at high tide.
The basis of the talk (by Jason Debney) was the work done by the Environment Agency in a project called TE2100. I had never heard of it. Its aims were to plan for the effects of increasing sea levels during the current century, and this talk was focussed on the area around Richmond (the Upper Tideway – which is very much the stamping ground of the BCC).
Given the uncertainty of forecasts of the effects of global warming, and natural changes over this period, the research team postulated that the most likely result would be a rise of about 1 metre in sea level, with the possibility of an increase of 4 metres. They defined 3 different scenarios corresponding to different levels of tidal increase, and action plans to go with each, so that as reality unfolds, appropriate, pre-defined, actions can be taken.
If, for example, the rise is restricted to 1metre, the Thames barrier – with minor modifications – will still protect most of London. At 4 metres, however, a new defence will be needed further out in the estuary – which will be pretty expensive. (I didn’t realise that the barrier is deployed not only to stop tidal surges coming upstream, but also to hold back the tide when the Thames is in flood, thus allowing the water to flow unimpeded to the barrier, and then released with the outgoing tide.)
Richmond is particularly at risk from increased water levels, because there are many low-lying buildings, but also because Richmond is not only affected by high tides, but also by floods coming down the river. The combination of such floods as we have seen in recent years, and a higher tide level would be catastrophic.
In the opinion of the speaker, the answer to increasing floods is the increasing use of, and restoration of, existing flood plains. A good example is Syon Park, which has always been a flood plain, and has remained undisturbed for hundreds of years. Kew Gardens has apparently included in its ten-year forward plan a decision to breach the Thames Wall, and allow parts of the gardens to flood.
An area of particular interest is around Ham, where there is a large wild area on the banks of the Thames, which used to be a flood plain until it was used to dump rubble from the second world war. This caused the ground level to rise, and negates its use as a flood plain. It would seem sensible – albeit expensive and unpopular – to remove this rubble, and all the current flora, and return it to use as a flood plain, where a quite different set of flora and fauna would move in over the years. This would go a long way to protecting urban areas from the worst effects of high water by taking the top off the flood.
This concept of allowing areas of ground to flood at times of very high water was seen to be superior to the alternative of building ever higher walls along the banks. Not only would that destroy the landscape, but would also be very expensive and disruptive. It would also not solve the problem of runoff of water from the land, which would be trapped on the wrong side of the walls. Runoff, of course, is an increasing issue as more and more land is concreted over, so that falling rain has nowhere to go except immediately into the river. Using permeable material for carparks and the like is seen as an important mitigating step, which would allow rain to soak into the ground underneath.
The speaker’s conclusion was that the EA had done a great piece of work over the last few years, but now it had to come up with a range of plans and get commitment to them.
My brain is now empty, but you can find more information at the EA website
http://www.environment-agency.gov.uk/ and at
http://www.thamesweb.com/.
A search for ‘TE2100’ will also take you to these and other sites.
It seems to me to be a subject in which we ought to take an interest – I wonder what would be the impact of an extra metre of water on the Marina and the Dock in general.